Endocrinology 3

Section

Question

Answer

What is cretinism?

Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (congenital hypothyroidism) usually due to maternal hypothyroidism; i.e. it’s severe hypothyroidism in children.

In hypothyroidism, TSH levels are high, and free T4 levels are low. True or false?

True.

How is hypothyroidism treated?

Replacement therapy with levothyroxine for life.

What is myxoedema coma?

Myxoedema coma is a rare but life-threatening state of extreme hypothyroidism. The illness is characterised by very low body temperature without shivering, confusion, bradycardia, reduced breathing effort. Patients may also have hypotension, hyponatraemia, hypercapnia, and hypoxia.

How is myxoedema coma treated?

T3 and hydrocortisone (T3 is preferable to T4 due to its rapid onset of action).

What is “myxoedema madness”?

Also known as myxoedema psychosis, this is an uncommon consequence of hypothyroidism. A chronically under-active thyroid can lead to slowly progressive dementia, delirium, and in extreme cases to hallucinations coma, or psychosis, particularly in the elderly. The myxoedema part of the name simply refers to the non-pitting oedema common to hypothyroidism.

This occurs with Grave’s disease (10% of cases do not have Grave’s disease). It is characterised by exophthalmos (bulging eyes), lid retraction, pretibial myxoedema, and thyroid acropachy.

What is pretibial myxoedema?

An infiltrative dermopathy resulting as a rare complication of Grave’s disease. It presents as waxy, discoloured skin on the anterior aspect of the lower legs, spreading to the dorsum of the feet.

What is thyroid acropachy?

A rare dermopathy associated with Grave’s disease. It is characterised by soft-tissue swelling of the hands and clubbing of the fingers.

What is the role of beta-blockers in treating hyperthyroidism?

Propranolol (160mg daily) is used to treat many of the symptoms of hyperthyroidism, such as tremor, palpitations, anxiety, and heat intolerance.

What is the radioactive iodine uptake test?

A type of scan used in the diagnosis of thyroid problems, particularly hyperthyroidism. The patient swallows radioactive iodine in the form of capsule or fluid, and its absorption by the thyroid is studied after 4–6 hours and after 24 hours. Low uptake suggests thyroiditis, high uptake suggests Grave’s disease.

What is De Quervain’s thyroiditis?

Also known as “subacute granulomatous thyroiditis” or “painful subacute thyroiditis”. The symptoms are of hyperthyroidism (initially) and hypothyroidism. Patients may also suffer from painful dysphagia.

Both are part of a group of drugs known as thioureylenes. Carbimazole is a pro-drug which is converted to its active form – methimazole. Methimazole reduces the production of thyroid hormones (T3 and T4) by blocking the peroxidase enzyme required for the iodination of tyrosine. Propylthiouracil does the same thing but also has the additional effect of reducing the deiodination of T4 to T3 in peripheral tissues.

Radioiodine is used as a treatment for hyperthyroidism. How does it work?

The isotope 131I is used. It is given orally and is taken up and processed by the thyroid in the same way as the stable form of iodine. Eventually it becomes incorporated into thyroglobulin. The isotope emits both β radiation and γ rays. The γ rays pass through the tissue without causing any damage. The β particles however are absorbed by the tissue and exert a powerful cytotoxic action, resulting in the destruction of the cells of the thyroid follicles.

Are there any contraindications regarding radioiodine as a treatment for hyperthyroidism?

Since the isotope of iodine emits γ rays, people are advised to keep their distance from patients on this therapy. Contraindications therefore include pregnancy and breastfeeding.

What are the side-effects of radioactive iodine treatment?

50% of patients are rendered hypothyroid in 10 years.

What are the complications of a thyroidectomy?

Early postoperative bleeding causing tracheal compression and asphyxia is a rare emergency requiring immediate removal of all clips/sutures to allow escape of the blood/haematoma. Laryngeal nerve palsy resulting in problems in voice changes occurs in 1%. Transient hypocalcaemia occurs in up to 10%. Hypoparathyroidism can also occur (glands might be removed).

What is “thyroid crisis” or “thyroid storm”?

Thyroid storm or thyrotoxic crisis is a rare but severe and potentially life-threatening complication of hyperthyroidism. It is characterised by a high fever (often above 40°C), fast and often irregular heartbeat, vomiting, diarrhoea, and agitation. It has a mortality of 10%. Heart failure may occur and myocardial infarction is encountered. Death may occur despite treatment.

How is thyrotoxicosis in pregnancy treated?

Propylthiouracil is used (carbimazole is contraindicated as it crosses the placenta – also not given when breastfeeding).

A goitre is swelling of the neck or larynx resulting from enlargement of the thyroid gland, associated with a thyroid gland that is not functioning properly (i.e. hypo/hyperthyroidism).

What is a multinodular goitre and what are its implications?

It starts as a diffuse, symmetrical, simple goitre with normal TSH, T4, and T3 levels. It then becomes an irregular multinodular goitre with areas of focal hyperplasia (which have growth advantage). It is called “toxic” when it causes hyperthyroid disease. It can result in the largest goitres which might extend retrosternally, cause tracheal compression, dysphagia, vena cava obstruction, and hoarseness due to recurrent laryngeal palsy.

memorize

Question

Answer

What is the worry with regards to a solitary thyroid nodule?

Malignancy should be considered in any solitary nodule (however, the majority of such nodules are cystic or benign).

What is Riedel’s thyroiditis?

Also referred to as a “fibrotic goitre”, Riedel’s thyroiditis is a rare condition characterised by a replacement of the normal thyroid parenchyma by a dense fibrosis that invades adjacent structures of the neck and extends beyond the thyroid capsule. This makes the thyroid gland stone-hard and fixed to adjacent structures.

What is “fine-needle aspiration”?

Fine needle aspiration is a diagnostic procedure used to investigate superficial lumps or masses. In this technique, a thin, hollow needle is inserted into the mass for sampling of cells that, after being stained, will be examined under a microscope. It can be used to check for malignancies in goitres.

A multinodular goitre has what % chance of being cancerous?

1-2%.

A large nodule within a multinodular riedel’, or a large nodule within a smooth goitre, has what % chance of being cancerous?

10-20%.

With regards to a thyroid scan, what is the difference between a “hot” and a “cold” nodule? What is their link to cancer?

Hot nodules are functioning (i.e. produce excess thyroid hormone) whereas cold nodules are non-functioning. A hot nodule is only rarely malignant; however, a cold nodule is malignant in only 10% of cases.

What is papillary thyroid carcinoma, how does it spread, and what is the prognosis?

The most common type of thyroid cancer. The lesion is multifocal (i.e. arises from many sites or locations). It presents mainly in women aged 20-55. Spread is local but sometimes to lung/bone. Prognosis is excellent, even if it spreads.

What is follicular thyroid carcinoma, how does it spread, and what is the prognosis?

A type of thyroid cancer that occurs more commonly in women over the age of 50. There is a single encapsulated lesion. It can metastasise to lung/bone/brain via the blood. Prognosis is good.

What is medullary thyroid carcinoma, how does it spread, and what is the prognosis?

A form of thyroid carcinoma which originates from the parafollicular cells (C cells) which produce the hormone calcitonin. Spread is local but it can also metastasise to the mediastinal lymph nodes, liver, lungs, and bone. Prognosis is very variable (but mainly poor).

What is anaplastic thyroid carcinoma, how does it spread, and what is the prognosis?

An aggressive thyroid cancer that has rapid development of hard, symmetrical goitres. It rapidly invades surrounding tissues (such as the trachea). This type of carcinoma is very resistant to cancer treatments and prognosis is therefore poor, although radiotherapy may help.